Electrical measuring instrument.



PATENTED NOV. 13, 1906.

P. HOLDEN. ELBGTRIGAL MEASURING INSTRUMENT.

APPLICATION i'iLED JAN-2. 1904.

UNITED s rrnsra'rnnr orricn.

FRANK. HOLDEN, OF RUGBY, ENGLAND, ASSIGNOR TO GENERAL ELECTRIC COMPANY,A CORPORATION OF NEW YORK.

ELECTRICAL MEASURING INSTRUMENT.

Specification of Letters Patent.

I Patented Nov. 13, 1906.

Application filed January 2, 1904- Sarial No. 187,456.

i which the following is a specification.

. My invention relates to electric measuring instruments of themovingcoil type employed for the measurement of continuous currents, andhas for its object to simplify and cheapen the construction of suchinstru ments by obviating the necessity of attaching polar extensions tothe magnets and at the same time to provide a form of instrument inwhich the moving coil is capable of movement through'a large range.

The accompanying drawings serve to illustrate my invention.

' Figure 1 is an elevation of an electric meter of the moving-coil typefitted with my improvements. Fig. 2 is a cross-sectional view of themagnetic system of the meter illustrated in Fig. 1. Figs. 3 and 4 areside elevation and section, respectively, of another modification of myinvention. Fig. 5 is an enlarged detail view showing the method ofmountingthe indicating-pointer.

In carrying out my invention according to the modification illustratedin Figs. 1 and 2, I provide a pair of ring-magnets c of flat rectangularsection. and conveniently of substantially oval form, the oval havingstraight sides with semicircular ends. The polepieces of each magnet areconstructed by interrupting eac'h ring across its axis at or about oneof the junctions of a semicircular end with a corresponding straightportion, as

shown at I), Fig. 1. superposed with The two rings are then the air-gapsoccupying relatively opposite positions, so that semicircular pole-facesopposite polarity confront each other.

A suitable number of distancepieces (Z, of i on or other suitablematerial, .are fastened between the rings, so as to hold them securelyin position relatively to each other. ,Thedistance between theconfronting ole-faces is small relatively to the length of t e gapsacross the axis of the rings,,so that an intense field shunted acrossthe space betweenthe said confronting pole-faces is produced, which issubstantially uniform over the Whole length of the pole-faces, Thissides.

field forms the working field of the instru ments and operates on thecurrent in a light coil e, surrounding one of the pole-pieces, so as toproduce movement of the coil in the di-' rection along the axis of thesaid pole-piece. This coil is carried on the extremity of a balancedindeX-pointerf, which is pivoted on an axis fitted with the usualcontrolling-springs g, and indicates the movement of the coil e on thegraduated scalesl. The axis of this pointer is pivoted between twocross'bars 72,

supported at each side by short columns 7c, of insulating material,which are carried by inwardly-projecting portions ofthe distancepiecesat, thus forming a very compact and ilr iexpensive construction, asclearly shown in According to the modification of my inventionillustrated in Figs. 3 and .4, I employthree superposed ring-magnets aof the form above described. The air-gaps 1) across the axes of the twoouter magnets are similarly disposed with regard to each other, but oppositely disposed with regard to the intermediate ring, so that thesemicirr ular polar extremity of the latter has two pole-faces ofopposite polarity confronting it on opposite The moving coil 6.surrounds the curved pole-pieces of the intermediate magnet, so that itis subject to the'field-across the two gaps on opposite sides of thesaid. polepiece. In this case the intermediatemagnet is preferably oflarger section than the two outer magnets, as shown in Fig. 4:, as itrequires to carry a larger magnetic flux. This form of magneticstructure maybe employed in the construction of an astatic instrument byproviding two moving coils secured to the same pivoted pointer, thesecoils embracing the curved pole-pieces of the two outer magnets.

In instruments constructed in accordance with my invention I preferablysoften the magnet-steel at polar extremities, so as to increase thepermeability of the latter, and therefore obtain greater uniformity offield.

What claim asnew, and desire to secure by Letters Patent of the UnitedStates, is 1. In an electric measuring instrument, two similar permanentmagnets, each having a pole end bent lengthwise of the magnet in the arcof a circle, mounted in reverse relative positions with the curved poleends in parallel planes confronting each other, and a moving coil withinthe air-gap between the curved pole ends.

In an electric measuring instrument, two similar permanent magnets, eachhavii'ig irmrel ole end bent lengthwise of the magnet inv the aic f acircle, mounted in re-- verse relative positions with the curved poleends in parallel planes i confronting each other, and a moving coilextending within the air-gap so formed pivoted on the axis about whichthe ends of the magnets are the are of a circle, mounted inreverse rclative positions with the curved pole ends in parallel planesconfronting each other, a

shaft rotatable on the axis about which the ends of the magnets arebent, and a measuring-coil mounted on the shaft and encircling one ofthe pole ends and movable thoreovor.

5. In an electric measuring instrument, two similar permanci'it magnets,each having a pole end bent iengthwise of the magnet in an arc of acircle, and distanceacres of .mag netic material, said magnets beingsecured together in reverse relative positions with the distance-piecesbetween them so as to form narro r air-gap 01* large area between thecurved pole ends.

6. In an electric measuring instrument, two sumlar permanent magnets,each having a pole end bent lengthwise of the magnet in an arc of acircle, and dista11ce-pieces of magnetic material, said magnets beingsecured together in reverse relative positions with the distance-piecesbetween them, a moving coil encircling one of the curved pole ends, andan indicator operatively connected to said coil.

7. In an electric measuring instrument, two similar permanent magnetshaving overlapping pole ends of opposite polarity ar ranged in parallelplanes, and a coil moving within the air-gap between said pole ends,said field-magnets bein made of hard steel and said pole ends of so itsteel.

8. In an electric measuring instrument, two similar permanent magnetscomposed of hard stool each having a soft-steel pole end arranged in aplane parallel to and confronting a pole end of opposite polarity on theother magnet, and a coil moving within the air-gap between said poleends.

9. in an electric measuring instrument, a permanent magnet having one ofits pole ends composed of soft steel, a second permanent magnet of hardsteel and having one of its pole ends composed of soft steel, said poleends being arranged parallel to and confronting each other, and a coilmoving within the air-gap between said. pole ends.

10. A magnet of hard steel having pole ends of soft steel integraltherewith.

ll. A permanent magnet having a body 75 portion of hard steel andsoftened pole ends integral therewith.

I .witncss whereof I have hereunto set my hand this 15th day ofDecember, 1903.

FRANK HOLDEN Witnesses it. WEsTAeoTT, ALFRED NUTTING.

